The present invention relates to multi-processor computer systems and, more specifically, to multi-processor computer systems that incorporate special mode processors.
A trend in the computer industry has been to develop computers that utilize faster processors, have greater through-put and support larger physical memories. The size of available fast access memory is dependent on the size of the processor""s address bus. For example, both Intel and AMD produce commercially available processors that have a thirty-two bit address bus and, therefore, support 232 or 4 Gbytes of physical memory. If more memory is required, however, a user must (1) resort to slow disk memory or (2) purchase a processor with a larger address bus, e.g., 64 bits. Processors with larger address buses are undesirably expensive and are unsupported by current commodity operating systems (as discussed below). Thus a need exists to increase fast access memory beyond 4 GB (i.e., conventional 32 bit address) in a cost effective manner.
Several well known operating systems have been developed for processors that utilize a 32 bit address bus and these include Windows NT of Microsoft Corporation and several UNIX implementations and the like. Since these operating systems are widely available they are referred to herein as xe2x80x9ccommodityxe2x80x9d operating systems.
In an attempt to provide more fast access memory (amongst other features), processors with enhanced or special modes of operation have been developed. One example of a special mode is the physical address extension mode of the Pentium Pro family of processors. PAE mode allows a processors 32-bit virtual address space to map to a 36-bit physical address space. This is accomplished by requiring a drastically different format for page tables than is required with a normal 32-bit physical address space. While this mode has potential, it has not been exploited commercially because of the lack of a commodity operating system that supports it. Software vendors have decided to wait for 64 bit processors rather than write new operating systems, etc., for the apparent stop gap 36-bit physical address mode and the like.
Accordingly, it is an object of the present invention to provide an increased amount of addressable memory space in a computer system.
It is another object of the present invention to provide a computer system that has a multiplicity of processors that operate in different modes.
It is also object of the present invention to increase the amount of addressable memory space in a computer system in a cost effective manner and without increasing the size of the address bus.
These and related objects of the present invention are achieved by use of a computing apparatus and method having an adjunct processor as described herein.
The attainment of the foregoing and related advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following more detailed description of the invention taken together with the drawings.